I bought a GameCube for Metroid Prime. Even if all I ever did was play that one game it would have been worth it to me. It brought me back to Nintendo after skipping out on the N64 and I’ve never looked back.
That’s probably the only case, though. Sony would have to have like 3-4 must plays for me and Xbox would have to have 8-10 for me to consider purchasing one of their consoles.